A photosensitive material comprising a photoconductive layer containing a phthalocyanine compound and a binder resin provided on a conductive substrate has been used in fields such as printing, etc. Particularly, in the field of printing, this material is subjected to corona charging, subjected to an image exposure using semi-conductor laser light having an oscillation wavelength at 780 nm as a light source to form an electrostatic latent image, and then a toner is bound thereon to visualize the latent image. By eluting the part other than the part on which the toner was adhered, a printing plate is formed.
This elution of the part other than the part on which the toner was adhered, i.e. a so-called development is conducted exclusively with an aqueous alkali solution. Therefore, it is necessary to impart alkali-solubility to the binder resin. Heretofore, it has been considered to be important to introduce a large amount of hydrophilic functional groups (e.g. hydroxyl group, acid anhydride group, carboxyl group, sulfonic group, etc.) so as to impart alkali-solubility to the binder resin. For example, in Japanese Laid-Open Patent Publication Nos. 2-210448 and 5-19514, there are described those in which a phthalocyanine compound, guanidine, etc. are dispersed in an alkali-soluble binder resin such as carboxylated polyvinyl acetate resin, styrene-maleic acid copolymer resin, etc. Further, in Japanese Laid-Open Patent Publication No. 4-212967, there are described those in which a phthalocyanine compound is dispersed in an alkali-soluble binder resin such as carboxyl-group containing acrylic resin, etc.
However, in any design of the binder resin, it is considered to be important to impart alkali-solubility, as well as improve dispersibility of phthalocyanine as a photoconductive substance. Otherwise, sufficient performances are not obtained in fundamental characteristics such as charging properties, etc. The photoconductive substance, particularly phthalocyanine has surface hydrophobic nature and, therefore, it can not be easily dispersed in a strong hydrophilic binder. Also, storage stability of a paint is inferior. Further, since the above hydrophilic functional group is absorbed on/adjacent to the surface of a phthalocyanine pigment, insulating properties of the photoconductive layer are insufficient, thereby affecting electrical characteristics (particularly, initial potential and dark decay at the time of corona charging).
Under these circumstances, the present inventors have studied intensively in order to solve the above problems, and the present invention has been accomplished.